In summary, our results indicate that the induction of human interferon in fibroblast cells, poly(rI.rC), is a multi-step process which involves derepression of the cellular genome and formation of interferon mRNA. The synthesis of interferon by these cells parallels synthesis of its mRNA thus indicating that interferon is synthesized as a response to its mRNA and immediately released from the cells. The interferon mRNA can be translated with fidelity both in Xenopus oocytes and cell-free systems. The product of in vitro synthesis stimulated by interferon mRNA isolated from fibroblast cells has the same antigenic specificity and similar electrophoretic mobility as interferon produced by these cells in tissue culture. Our results further indicate that the antiviral effect of interferon is a membrane phenomenon in which cellular gangliosides may play an important role. BIBLIOGRAPHIC REFERENCES: Reynolds, F. H., Jr. and Pitha, P. M. Molecular Weight Study of Human Fibroblast Interferon. Biochem. Biophys. Res. Commun. 65:107, 1975. Reynolds, F. H., Jr., Premkumar, E., and Pitha, P. M. Interferon Like Activity Produced by Translation of Human Interferon Messenger RNA in Cell-Free Ribosomal Systems and in Xenopus Oocytes. Proc. Nat. Acad. Sci. 72:4881, 1976.